The need for reducing the cost of injecting payloadmass into orbit is the main stimulating factor for further modifications and creation of new launch vehicles.
降低将有效载荷送入轨道的成本的需求是刺激现有运载火箭进一步改型和新型运载火箭研制的主要因素。
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Having initially connected the ornithopter using a DC power source, they realized that the device could lift 1.5 grams of payload, which was roughly the mass of the batteries required for flight.
But chemical-based systems are severely limited by the fact that the vehicle mass must be made mostly of propellant, which leaves little room for the payload.